迅速鋳造用石膏系埋没材の膨張特性と加熱開始時間が鋳造精度に及ぼす影響
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概要
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The purpose of this study was to investigate the effects of the expansive behaviors and the heating start time following initial mixing of gypsum-bonded investments for quick heating on casting accuracy of crowns using a three-dimensional coordinate measurement system. For the experiments, four types of quick heating type investment (Cristoquick II : QII, Cristobalite New F-1 : F1, Cristobalite Q : CQ, Cristobalite PF : PF) and one type of conventional gypsum-bonded investment (Cristobalite Micro : CM) were used. In the experiments, the setting expansion and thermal expansion of the investments were measured, and for the quick heating types, the thermal expansion by changing the heating start time to 30 minutes, 45 minutes, and 60 minutes after initial mixing of the investments was also measured. The wax patterns were made using crown-type dies, and the outside and inside shapes of the patterns were measured using the three-dimensional coordinate measurement system. The origin of coordinates during measurement was set so that it would be at the center of the sprue erected vertically at the center of the engaged surface of the wax patterns. The casting accuracy of the castings was measured using the measurement result of the die as the design value. The casting accuracy of the castings obtained using the conventional investment was used as the control. The following results were obtained. 1. The setting expansion of all the quick heating types was larger than that of the conventional type. On the other hand, their heating expansion was smaller than that of the conventional type, and no significant difference was recognized even when the heating start time after initial mixing of investment was changed. 2. The dimensional change of the castings tends to expand both inside and outside, with the tendency stronger inside, and the dimensional change of the castings in the die top was smaller than that in the die bottom. 3. The dimensional change of the height of the castings tends to expand in comparison with the wax pattern, and the tendency was stronger in comparison with the dimensional change of the side. The tendency was stronger for the quick heating types than for the conventional type. 4. The casting accuracy obtained using the conventional type was 0.41 to 0.59%, and that of the quick heating types was 0.36 to 0.52% for QII, and 0.16 to 0.29% for PF when the heating after 30 minutes from initial mixing, 0.41 to 0.75% for QII, and 0.15 to 0.40% for PF after 45 minutes, and 0.42 to 0.76% for QII, and 0.20 to 0.51% for PF after 60 minutes.
- 奥羽大学の論文
- 2003-09-30
著者
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